Northwest Dive Club

Finished up my first day of dives on my new Kiss GEM rebreather down here in Florida with my instructor
Doug Ebersole, a tampa area cardiologist, and premiere KISS GEM instructor. There is a really big
network in the SE of SCR users, with the inventor of the GEM nearby in Arkansas.

We discussed in depth the history of the GEM, the original GEM, the today GEM, and the tomorrow GEM.
I really wanted to make sure what I have learned about the GEM, was correct. As my long term goal is to
be able to dive it to 200ft. So looks like I'll be heading back down this way next summer for extended
training, as should be available by then (New scrubber and mouthpiece). These changes will bring the
GEM up to other SCR's in the world, as well as bring it into the world of tech diving. Fun!

So early morning, arrived at the shop, and we spent awhile getting my GEM fully setup on my backplate.
When through the checklist, and away we went.

So we headed off to Lake Denton, to do a confined space dive, and then a couple of dives.

Doug cautioned me the lake might be crowded, as its a central training area for all the shops. Now when
I think crowded, I think of Cove 2 training days, where there's maybe 20-25 divers. Bzzt!

When we arrived, out on the Lake I counted over 13 dive flags out there, and probably a 100 divers.

There's lots of room though, and our timing was about perfect, as alot of them were leaving throughout
our dives, to the point after finishing our last dive, we almost had the lake to ourselves. Todays dives
topped out about 50ft. Went over all the skills. Bail Out, reg swap, on/off loop, clearing the loop, etc.

The first dive, my counterlungs were to high, so it breathed abit tough, but ok. For the second dive,
lowered them,and was better. It breathes in ok, exhaling does take some effort.

I'd been warned by other rebreather divers, that switching to an SCR/CCR was a difficult transition, as buoyancy
is different from OC. I found that advice far from the truth, at least for me. I expected to wind up for
a dive or 2, to look like an epileptic octopus. Instead I found it very simple to dive, with the only real change
was you have to adjust buoyancy with the wing, not your lungs. I only very rarely ever hand sculled, and if I ever had to
make any correction, was a mild wrist movement, or fin twist.

The GEM is quite a gas extender though. In 2 40min dives, I only used 1100 psi of a 3500psi tank (100cf), so just
abit under 33cf in 2 dives. Sweet!

I noticed no trim issues at all.

Today we are heading to "The Springs" a 2 hour drive, and I'll get to dive a cavern, double sweet!

Doug's a good guy -- please say hello to him for me!

Sorry Lynnne, didnt read this until just now.

Today was dive day 2, we heading to Blue Grotto, in the springs, as all the dive boats were booked. I'm actually glad we went here instead, as it was super cool. My first introduction into a cavern system, with a few spots that were kinda tiny.

First dive was funny, as I was kinda going about, and then all of the sudden hit something, and I'm like "what the hell?" and reaslized it was the top of the first cavern. Oopsie! So after that I paid much more stricter attention, and never had that happen again. Just one more thing you have to think about. We dove the first dive down to about 90 ft, and as we were going down, I watched my PPO gettign really high, like 1.53 and climbing. Uh oh, checked to make sure my injector was only firing upon demand (it was), signaled Doug, and heading up about 20 feet, as it shouldnt have been that high. Yes, I'd calibrated the O2 sensor before the dive, and all my prechecks, prebreath, all were good. Now this was a brand new sensor, and had been left out to stabilize, but our precheck voltage was 8.4, which is just under the 8.5mv limit. But we thought it was close enough for the dive. Guess not.

After the dive, we swapped out the sensor, and next dive was fine, no PPo issues at all at depth. Strangely the first dive, we both used about 1100psi on that dive (I used 100 psi less than doug), but the next exact same dive profile, we each only used around 700psi. we're still not sure why so high the first dive, but we'll investigate later.

Blue Grotto was pretty cool for a cavern system, and those tight spots were tight enough for me, that I dont think cave diving will be in my future, these were tight enough. But caverns were hell'a cool.

I did learn on this dive, tha tmy unit breathes better when I'm in really good trim, and it I get much heads up at all, its a difficult exhale. So while ascending from the lower cavern system (90 > 40), I'd just stop, tuck my head down, and get a good exhale, and continue up if I needed to. Good thing to learn.

Doug and I spent more time on the 4 hours round trip diving talking about the Level 2 course, and making plans for coming down there again next summer. By then the level 2 course should be available, the new 8:1 mouthpiece,and bigger scrubber. BTW, the current 3:1 mouthpiece has about a 5% drop from the drive gas, the 8:1 should be interesting.

GEM urges you above 20ft to breath out the loop, or switch to OC. I found it almost un-neccessary, as we spent some time in teh 8-15ft range, and my PPo was just fine, never saw below .40 on my shearwater. Doesnt mean its ok to do it, but it means you can, if you are careful, and monitor it closely.

Since I learned Bob's Superman pose, my ShearWater is always in my face, so its easy to actively monitor.

And Koos, if you are reading this, I'm switching to the 7ft hose when I get back, as our gas sharing drill was pretty tough in a small cavern with a short hose.

Overall, I really like the GEM, its easy to dive, no trim adjust (side to side) at all, and the gas extension with my 120 tank will be way beyond a paltry set of doubles...

Interesting report. Thanks for writing about it. I'm very curious about the GEM; I only know of one other diver certified on it here. What are you using for drive gas? Air or 'trox? You don't carry any bailout with it, correct? Just an independent reg to go OC?

"Technically" (note emphasis) it runs on EAN32-40, with about a 5% drop in the loop. But... you can run anything in it. But that falls outside of any "current" training.(again, note emphasis ) So if you run anything outside of EAN 32-40 you may die, grow third eye, or some other evil thing may befall you if you operate the unit outside of training, or defined use.

With all that said, with a 5% drop in the loop, you would be just about hypoxic(appx16% O2) running just 21% air, thus a bad plan.

Your bailout is to switch to OC(backgas) but obviously you have to be aware that your OC backgas is at a higher percentage than your loop, so you wanna ascend quickly into the gases MOD.

There's nothing stopping you from plumbing in a gas switch block for a differnt bailout gas, or even a deep gas, but again, thats outside of "current" GEMs use and certified training and you may die if you do so:).

Warning: Anything I say here outside of GEM training and/or defined use is purely theorhetical and should be taken that way.

Or you can plumb in a gas suitable for the depth you're at so if you bail out you aren't exceeding your MOD. And accept the deco penalty associated with the drop in fO2.

OK ?? I read all the posts...now my head hurts !! What happened to Scuba ?? Breathe underwater ...enjoy the view.....play with fish....?

Blow-N-Bubbles wrote:OK ?? I read all the posts...now my head hurts !! What happened to Scuba ?? Breathe underwater ...enjoy the view.....play with fish....?

Nothing wrong with that at all.

Blow-N-Bubbles wrote:OK ?? I read all the posts...now my head hurts !! What happened to Scuba ?? Breathe underwater ...enjoy the view.....play with fish....?

Good point. Moving this topic to the advanced training forum.

spatman wrote:

Blow-N-Bubbles wrote:OK ?? I read all the posts...now my head hurts !! What happened to Scuba ?? Breathe underwater ...enjoy the view.....play with fish....?

Good point. Moving this topic to the advanced training forum.

Oops. Didn't even look at the header. My bad.

Jeff Pack wrote:Warning: Anything I say here outside of GEM training and/or defined use is purely theorhetical and should be taken that way.

Once bitten, twice shy, eh...

Anything Jeff says should be taken in the EXACT way you want to take it

hehe.. good report Jeff, looking forward to seeing you when you get back... I have a 7ft hose waiting for you..

CaptnJack wrote:Or you can plumb in a gas suitable for the depth you're at so if you bail out you aren't exceeding your MOD. And accept the deco penalty associated with the drop in fO2.

Except you have to remember the 5% drop in the loop, so you may have EAN 36, but on the loop breathing 31%.

If you arent deep, no big deal, but if you are deep, it can be a big deal.

kdupreez wrote:

Jeff Pack wrote:Warning: Anything I say here outside of GEM training and/or defined use is purely theorhetical and should be taken that way.

Once bitten, twice shy, eh...

Anything Jeff says should be taken in the EXACT way you want to take it

hehe.. good report Jeff, looking forward to seeing you when you get back... I have a 7ft hose waiting for you..

Cool, I need to do a tweak dive this weekend, first dive in Salt/Cold and drysuit. Hit me up if you wanna go.

Jeff Pack wrote:

CaptnJack wrote:Or you can plumb in a gas suitable for the depth you're at so if you bail out you aren't exceeding your MOD. And accept the deco penalty associated with the drop in fO2.

Except you have to remember the 5% drop in the loop, so you may have EAN 36, but on the loop breathing 31%.

If you arent deep, no big deal, but if you are deep, it can be a big deal.

The deeper you go, the less important the fO2 drop becomes - at least for the bottom phase of the dive. An fO2 drop during deco is a significant issue.

But if I'm at my MOD of my loop gas, and bail out to OC thats 5% more O2, thats a big deal.

On the GEM, you always have to know the MOD of your back gas, and you should also know the MOD of your loop gas
(95/116 if running EAN36/31(loop)).

Sort of a rule of thumb I was taught, was if you bail out to OC, just immediately ascend 20ft if your PPo was already high.

With the new 8:1 mouthpiece, that difference will be even more substantial. I dont know yet what the drop is on the new mouthpiece.

Who says you have to dive to the MOD of your loop? You're on an SCR so you don't have the benefit of optimum ppO2 for the whole dive - that's just life on SCR.

The 8:1 mouthpiece will have a pretty big drop, depending on how effective it is in the real world. You can figure it out with Doug and a calculator and its not pretty for bailout.